Use of chitosans for the treatment of nail inflammatory diseases

ABSTRACT

Chitosan-based nail formulations are useful to treat nail inflammatory diseases like psoriasis, atopic dermatitis and  lichen planus . The chitosan is normally in the form of an amino-polysaccharide derivative, preferably water soluble, such as hydroxypropyl chitosan. The formulation may be a nail lacquer, a spray, a cream, an ointment, a gel, a lotion or a foam and may have a content in chitosan, chitosan derivative or a salt thereof from 0.1 to 25 wt. % with respect to the total weight of the formulation.

The present invention relates to use of chitosan, a chitosan derivativeor a physiologically acceptable salt thereof, for the preparation of amedicament, or a medical device, or a sanitary product, or a cosmetic,in form of a nail lacquer, useful for the topical treatment ofinflammatory diseases of the nails, such as psoriasis, lichen planus andatopic dermatitis.

Psoriasis is a genetically predetermined hyperproliferative skindisease, characterized by increased cell proliferation, glycogenaccumulation and incomplete differentiation in the cells of theepidermis. Nail involvement in psoriasis is common and has been reportedin between 50% and 56% of cases. It is estimated that over a lifetimebetween 80% and 90% of psoriatic patients will suffer nail localizationof psoriasis (de Berker, Baran & Dawber: the nail in dermatologicaldisease. In: Baran & Dawber's: Diseases of the nails and theirmanagement. Baran et al Eds, 3^(rd) ed. Blackwell Science, 2001).Overall, 58% of patients with nail psoriasis consider that thiscondition interferes with their job and 52% describe pain as a symptom.Nail psoriasis is affecting adults and children. In children, nailinvolvement has been found to range between 7% and 39% according to thedifferent authors. In children with juvenile psoriatic arthritis, 80% ofchildren developed pitting, a nail manifestation of psoriasis.

Severe nail involvement may not imply severe psoriasis of the skin andthe type of the nail change is not associated with any particulardistribution of the skin lesions. The clinical signs of psoriasis can becorrelated with the site of involvement of the epidermal structures ofthe nail. The main psoriatic features in the nails are, in order offrequency:

-   1) pitting: pits are punctate depressions, usually small and    shallow, that can vary in size, depth and shape. They originate from    focal psoriasis of the proximal matrix (the region where the nail is    formed). Most pits are superficial, and when extensive they can    produce gross abnormalities in colour and texture, and can render    the nail fragile. Histologically, pits represent a defect in    superficial layers of the nail plate and when the psoriasis becomes    more marked, a pit may enlarge and produce a hole in the nail plate.-   2) discoloration of the nail: typical pictures are leuconychia    (white nail appearance), when the nail matrix is involved, or salmon    colour when the nail bed is involved. Psoriasis in the nail bed    produces oval, salmon coloured, oily spots of various size.-   3) onycholysis: this is a detachment of the nail plate from the nail    bed. This occurs mainly when oily spots affect the hyponychium (the    part under the nail plate) medially or laterally. Onycholytic nail    has a yellowish colour, due to a combination of air and the    accumulation of squames under the nail interface.-   4) subungual hyperkeratosis: this is a thickening of the tissues    under the nail plate. It is manifested as accumulated squames, and    is an expression of the alteration of the keratin composition in    nail bed psoriasis.-   5) nail plate abnormalities: they include serial transverse    depression, especially on the thumbs where they mimic washboard    nails. Other common abnormalities are longitudinal ridges of the    nail with bumps that resemble drops of melted wax.-   6) splinter haemorrhages: they occur in fingernails of 42% of    psoriatic patients with nail disease and in 6% of their toenails.    The sign reflects the orientation of the capillary vessels in the    nail bed and the proliferation and fragility of these capillaries in    active psoriasis.

There may be psoriatic scaling of the proximal nail fold with softtissue swelling or chronic paronychia. The changes observed in the nailplate depend on the location and duration of the disease process. Thelesions may reflect transient matrix dysfunction and be limited inextent, such as pits and transverse furrows. Alternatively, they mayrepresent persistent disease and result in sustained nail abnormalities,such as loss or thickening of the nail plate. Besides the aestheticappearance, the psoriatic nails are fragile and painful, and patientsare prevented from their daily life activities.

The treatment of the nail psoriasis includes systemic and/or topicaltherapies. Systemic therapies include potent corticosteroids, Vitamin Danalogues, retinoids or immunosuppressive agents, and are generallyavoided due to their potential toxicity, unless the patient presents avery severe, generalized psoriasis.

Topical therapies are mainly for application to the base of the nail. Atthis site, they may treat psoriasis of the nail fold and penetratethrough the underlying matrix to a limited extent. Some of thetransverse ridging in the psoriatic nails is associated withinflammation of the proximal nail fold. If this is reduced, the matrixfunction returns towards normal and nail ridging diminishes. Ifonycholysis is present, the nail plate must be trimmed back to the pointof separation.

Topical products used in psoriasis are the following:

-   1. corticosteroids: fluocinolone acetonide, triamcinolone acetonide,    bethametasone salts, clobetasol propionate, are known in the art.    All of them are applied under occlusive medication, and side effects    such as distal phalangeal dystrophy have been reported (Deffer &    Goette Archives of dermatology, 1987, 123:571-572. Requena et al.    Archives of dermatology, 1990, 126:1013-1014).-   2. calcipotriol: according to some literature reports (Kokely et    al., 1994, J. Dermatol. Tretment, 5:149-150) topical calcipotriol    may be useful as treatment of nail psoriasis. The limit of this    therapy is represented by need of occlusive medication, which is    bothersome for the patients, and risk of severe systemic side    effects, due to the impairment of renal function and calcium    metabolism, thus this drug is not recommended e.g. in children.-   3. cyclosporin: topical cyclosporin was used in a single subject,    applying a 10% oily preparation under occlusive medication for    several months, with clinical benefit (Tosti A., Dermatologica,    1990, 180:110).-   4. retinoids: topical use under occlusive medication of a tazarotene    cream gave clinical benefit (Bianchi et al. Br J Dermatol. 2003,    149:207-9).

All topical treatments of nail psoriasis in the art are characterized bythe need of occlusive medication, which is bothersome for the patient,impairs their quality of life and may be applied in practice only in thenight hours. Thus, there is a strong unsatisfied need for new effectivetherapeutic agents, simple to use and safe enough to allow chronic useby patients. Lichen planus is also an inflammatory disease of the skin,with evidence of a genetic susceptibility, probably due to an immuneimbalance, often associated with systemic involvement (de Berker, Baran& Dawber: the nail in dermatological disease. In: Baran & Dawber's:Diseases of the nails and their management. Baran et al Eds, 3^(rd) ed.Blackwell Science, 2001).

Lichen planus may involve the nail plate by appearing in the followingclinical subtypes:

-   1) typical lichen planus-   2) twenty nail dystrophy-   3) idiopathic atrophy of the nails

When a nail fold disease is present, this indicates that the proximalnail matrix is involved and nail plate changes are likely to occur soonafterwards. The nail gradually reflects the disease process with alongitudinal red line indicating a thinning nail plate, evolving todistal splitting, where it is most fragile. The next stage is completesplit.

Ulceration, hemorrhagic erosions and scarring may appear. Pitting isalso a manifestation of lichen planus of the proximal nail matrix.Lichen planus seldom involves exclusively the nail bed and features ofnail bed disease include hyperkeratosis and onycholysis.

The prognosis depends on the degree of matrix involvement and scarring.Complete involvement of nail matrix and nail bed will produce a totalloss of the nail plate and permanent atrophy with scarring. Treatment issymptomatic, including oral corticosteroids, retinoids and azathioprine.Severe non-scarring types may be helped by topical treatment with potentcorticosteroids.

Of course, nail inflammatory diseases are chronic conditions, that donot respond definitely to a therapeutic treatment. Thus, as for skin,the ideal treatment is lifelong and is put in practice as two or moretherapeutic cycles per year for the patient's life.

Chitosan derivatives are amino-polysaccharides, derived from the chitinextracted from the exoskeleton of the crustaceans, known in the art fortheir use in different preparations for skin. KR20020084672 discloseschitosan as an ingredient of microspheres, useful as a carrier forseparation of proteins or peptides; KR20020048534 reports chitosan as aningredient of a pack composition for skin massage, including paraffinwax as an effective component; JP2005306746 is teaching the use ofchitosan to obtain a wrinkle therapeutic agent as an ingredient ofgel-like or spongy preparations of botulinus toxin. WO2005055924 reportschitosan derivatives as ingredients of hydrogels useful forcavity-filling wound dressings. JP2004231604 teaches compositions ofchitosans having a high deacetylation degree, as an ingredient of acarrier sheet with a porous spongy texture. WO03042251 disclosescompositions comprising chitosan in the form of a network of nano-sizedfibres. WO02057983 discloses a multi-layered, air gap sheet of chitosanwith a regular lamellar structure which retains drugs for a prolongedperiod of time; JP11060605 teaches an amphiphilic chitosan derivativewhich can be used as dispersion stabilizer or emulsifier in a drug forapplication to skin. US2004043963 discloses chitosan conjugated linoleicacid and a chitosan conjugated Vitamin A for the preparation ofcompositions for treatment of inflammatory skin diseases, includingatopic dermatitis, eczema and psoriasis. Moreover, EP1303249 reports theuse of water soluble chitosan derivatives as film forming ingredients ofnail lacquers, including antimycotic agents for the treatment of nailfungal infections, whereas WO2004/112814 discloses a nail restructuringcomposition based on one herb extract from the genus Equisetum incombination with hydroxypropylchitosan, which is used as a film formingagent. The use of chitosans as film forming agents is also disclosed inWO2006111426 and in WO2007042682.

WO03051376 discloses the use of chitosan oligomers having a molecularweight of less than 10000 Da for preventing or reducing inflammation orhypersensitivity.

None of the references known in the art reports any activity ofchitosans or chitosan amino-polysaccharides in nail inflammatorydiseases, chitosans having being used until now as carriers of activesin various diseases or as a film forming agent in mycotic infections.

It has now surprisingly been found that chitosans, chitosanamino-polysaccharides and/or physiologically acceptable salts thereof,are useful for the topical treatment of inflammatory diseases of thenails, such as psoriasis, lichen planus, alopecia areata and atopicdermatitis. Chitosans and chitosan amino-polysaccharides permeate thekeratin structures and reach the nail matrix, where the defect ofkeratinisation occurs during inflammatory diseases, by decreasinginflammation at that level, thus by allowing the growth of a healthy,smooth nail. When chronically applied onto the nail surface, naillacquers containing chitosan or its derivatives result in a decrease ordisappearance of pitting and of desquamation, thus rendering the nailless fragile and reducing pain.

Nail lacquers based on chitosan and/or chitosan derivatives, such aschitosan amino-polysaccharides, are simple to use and safe enough toallow chronic application by patients. Moreover, the nail lacquers maycontain other agents active on nail inflammation, thus strengtheningtheir activity and allowing a long lasting adherence to the nailsurface, suitable for long lasting release to the nail, avoidingocclusive medications.

DESCRIPTION OF THE INVENTION

The object of the present invention is the use of chitosan, a chitosanamino-polysaccharide and/or a physiologically acceptable salt thereof,for the topical treatment of inflammatory diseases of the nails, such aspsoriasis, lichen planus and atopic dermatitis.

The preferred chitosan amino-polysaccharides are water soluble and havea molecular weight higher than 50000 Da, preferably of from 100000 to500000 Da; among them hydroxyalkyl chitosans, such as hydroxypropylchitosan, and carboxyalkyl chitosans are particularly preferred.

Nail lacquers based on chitosan or chitosan amino-polysaccharides, inthe form of solutions, emulsions, colloids, or suspensions, with acontent in chitosan or chitosan amino-polysaccharide from 0.1 to 10 wt.%, more preferably from 0.2 to 5 wt. %, most preferably from 0.3 to2.0%, are suitable to significantly improve the nail dystrophy inpatients with inflammatory diseases of the nails, such as naillocalization of psoriasis, by decreasing fragility, pain and pitting,and improving the cosmetic appearance of the nails.

Pharmaceutical compositions will be prepared according to conventionaltechniques, using compatible excipients and pharmaceutically acceptablecarriers, and may contain, in combination, other active principles withcomplementary or, in any case, useful activity. Examples of thesecompositions prepared according to the present invention include:solutions, emulsions, suspensions, colloids, for application to nails.

The compositions according to the present invention may contain one ormore active agents from corticosteroids, immununo-suppressants,antipsoriatic agents, keratolytics, retinoids, plant extracts, and aresuitable to treat nail inflammatory diseases, such as psoriasis, atopicdermatitis, and lichen planus.

Examples of corticosteroids which may be included in the composition inaccordance with the present invention include 21-acetoxypregnenolone,alclometasone or its dipropionate salt, algestone, amcinonide,beclomethasone or its dipropionate salt, betamethasone and saltsthereof, including, for example, betamethasone benzoate, betamethasonedipropionate, betamethasone sodium phosphate, betamethasone sodiumphosphate and acetate, and betamethasone valerate; clobetasol or itspropionate salt, clocortolone pivalate, hydrocortisone and saltsthereof, including, for example, hydrocortisone acetate, hydrocortisonebutyrate, hydrocortisone cypionate, hydrocortisone phosphate,hydrocortisone sodium phosphate, hydrocortisone sodium succinate,hydrocortisone tebutate and hydrocortisone valerate; cortisone acetate,desonide, desoximetasone, dexamethasone and salts thereof, for example,acetate and sodium phosphate; diflorasone diacetate, fludrocortisoneacetate, flunisolide, fluocinolone acetonide, fluocinonide,fluorometholone, flurandrenolide, halcinonide, medrysone,methylprednisolone and salts thereof, e.g. acetate, sodium succinate;mometasone furoate, paramethasone acetate, prednisolone and saltsthereof, e.g., acetate, diethylaminoacetate, sodium phosphate, sodiumsuccinate, tebutate, trimethylacetate; prednisone, triamcinolone andderivatives thereof, e.g. acetonide, benetonide, diacetate,hexacetonide.

Examples of immunosuppressant agents which may be included in thecomposition in accordance with the present invention include:cyclosporin, tacrolimus, pimecrolimus and sirolimus.

Examples of antipsoriatic agents which may be included in thecomposition in accordance with the present invention include: anthracenederivatives, such as dithranol; psoralens, like trioxsalen ormethoxsalen; Vitamin D3 analogues, like calcitriol, calcipotriol ortacalcitol; retinoids, like retinoic acid, tretinoin, isotretinoin,etretinate and acitretin, tazarotene; fumaric acid and esters thereof,e.g. monomethyl ester, dimethyl ester. Keratolytics are peeling agents,useful to remove the horny outer layer of the skin, i.e. to promote theremoval of dead skin cells from the stratum corneum. Examples ofkeratolytics which may be included in the composition in accordance withthe present invention include: salicylic acid; benzoyl peroxide.

The compositions according to the present invention are applied onto thenail surface by brush, or by a plate applicator, or by spray.

The pharmaceutical compositions and the uses of the present inventionwill now be more fully described by the following examples. It should,however, be noted that such examples are given by way of illustrationand not of limitation.

EXAMPLE 1

A nail lacquer having the following composition wt./wt. % is prepared:

1. purified water 21.0% 2. ethanol 73.0% 3. ethyl acetate 4.0% 4.hydroxypropyl chitosan (HPCH) 1.0% 5. cetostearyl alcohol 1.0%

Preparation

The formulation is prepared by using a closed vessel with a stirrer. Tothis vessel are added ethanol, deionized water and ethyl acetate to forma mixture. Thereafter, cetostearyl alcohol is added. Finally,hydroxypropyl chitosan is added and the resulting mixture is stirred for24 hours or until dissolution.

The obtained composition has a clear and homogenous appearance evenafter prolonged storage. Moreover, when applied on the nails, the liquidis able to form a matte, non-sticky and elastic film which couldstrongly adhere to the nail surface.

EXAMPLE 2

A nail lacquer having the following composition wt./wt. % is prepared:

1. purified water 29.375%   2. ethanol 96° 70.0%  3. budesonide 0.025% 4. hydroxypropyl chitosan (HPCH) 0.5% 5. Peg-40 Hydrogenated castor oil0.1%

Preparation

The formulation is prepared as per the Examples 1 and 3, by addinghydroxypropyl chitosan as the final ingredient and stirring for 24 hoursor until dissolution.

EXAMPLE 3

A nail lacquer having the following composition wt./wt. % is prepared:

1. propylene glycol 13.0%  2. isopropanol 82.497%   3. calcitriol0.003%  4. ethyl acetate 4.0% 5. chitosan 0.5%

Preparation

Chitosan is dissolved in propylene glycol, then calcitriol previouslydissolved in isopropanol is added. Then ethyl acetate is added and theresulting mixture is stirred until dissolution.

EXAMPLE 4

A nail lacquer having the following composition wt./wt. % was prepared:

1. purified water 29.35% 2. ethanol 96° 70.00% 3. hydroxypropyl chitosan(HPCH) 0.50% 4. betamethasone-17-valerate 0.05% 4. PEG-40 hydrogenatedcastor oil 1.00%

Preparation

The formulation was prepared by using a suitable closed vessel providedwith a stirrer. To this vessel were added ethanol, betamethasone-17-valerate and PEG-40 hydrogenated castor oil. The mixture was stirredand then water was added. After short stirring hydroxypropyl chitosanwas added. The mixture was stirred for 24 hours until completedispersion of hydroxypropyl chitosan. The resulting composition islimpid, colourless liquid, with typical alcoholic odour.

EXAMPLE 5

A nail lacquer having the following composition wt./wt. % was prepared:

1. purified water 29.0% 2. ethanol 96 60.0% 3. hydroxypropyl chitosan(HPCH) 0.5% 4. cyclosporine 5.0% 5. urea 5.0% 6. Polyethylenlycol 4000.5%

Preparation

The formulation was prepared by using a suitable closed vessel providedwith a stirrer. To this vessel were added water, ethanol, and aftershort stirring cyclosporine. The complete dissolution was immediate.Then urea was added, and, after dissolution, Polyethylenglycol 400 wasadded. After 10 min stirring hydroxypropyl chitosan was added. Themixture was stirred for 8 hours until complete dissolution ofhydroxypropyl chitosan. The resulting composition was a limpid,colourless liquid, even after prolonged storage.

Moreover, the liquid was able to form a matte, non-sticky and elasticfilm which could strongly adhere to the nail surface.

EXAMPLE 6

A nail lacquer having the following composition wt./wt. % was prepared:

1. purified water 19.45% 2. propylene glycol 10.00% 2. isopropanol70.00% 3. chitosan 0.50% 4. bechlometasone dipropionate 0.05%

Preparation

The formulation was prepared by dissolving chitosan and bechlometasonedipropionate in propylene glycol, then adding the other ingredients, andstirring the mixture until dissolution. The resulting liquid was able toform an elastic film which could strongly adhere to the skin surface.

EXAMPLE 7

A nail lacquer having the following composition wt./wt. % was prepared:

1. purified water 52.0% 2. ethanol 36.5% 3. diethylenglycolemonomethyleter 0.5% 4. methylsulphonylmethane (DMSO₂) 5.0% 5.hydroxypropyl chitosan (HPCH) 1.0% 6. Equisetum arvense glycolic extract5.0%

Preparation

The formulation was prepared by using a suitable closed vessel providedwith a stirrer. To this vessel were added ethanol, deionized water anddiethyleneglycol-monomethylether to form a mixture. Thereafter, afterdissolution thereof, Equisetum arvense glycolic extract andmethylsulphonyl methane were added. Finally, hydroxypropyl chitosan wasadded and the resulting mixture was stirred for 24 hours or untildissolution.

The obtained nail lacquer composition had a clear and homogeneousappearance and a yellowish color even after prolonged storage. Moreover,the lacquer was able to form a matte, non-sticky and plastic film whichcould strongly adhere to the nails. When applied, the moisture and airpermeable lacquer did not burn or cause irritation on the adjacent skinor the periungual bed.

EXAMPLE 8

An open, controlled clinical study was performed to assess the efficacyand the safety profile of the nail lacquer according to the Example 7 onpatients with nail psoriasis. The involved patients were 20 women and 10men, aged between 18 and 75 years (mean 46.5 yrs) affected by nailpsoriasis, with symmetric lesions of both sides. The nail alterationswere manifest from 6 months-2 years prior to the inclusion into thestudy, with the following clinical characteristics: presence ofpitting=15%; presence of onycholysis=9%; presence of leuchonychia=6%.The severity of the nail psoriasis, measured by the NAPSI score (Nailpsoriasis severity index, according to Baran R., Br J Dermatol, 2004,150:568-569; Parrish et al., J Am Acad Dermatol, 2005, 53:745-476), wasbetween 2 and 5. The nail lacquer according to the Example 7 was appliedonce daily by the patients on the fingernails of the left hand for 24consecutive weeks. No other systemic or topical antipsoriatic treatmentwas taken by the patients during the whole treatment period. At the end,the therapeutic efficacy was judged by the investigator by a clinicalexamination at cold light, and compared to the fingernails of the righthand. At the end of 24 treatment week, the result of the treatedfingernails was judged as “excellent” in 18 cases, “good” in 5 cases and“none” in 5 cases, while the untreated hands were unmodified compared tobaseline. The remaining 2 cases were lost to follow up. The quality oflife of patients, measured by Dermatology Life Quality Index (DLQI) is asimple 10-question validated Quality of Life questionnaire (Finlay &Khan: Clinical and Experimental Dermatology, 1994, 19:210-216 related tothe treated hand, also resulted as much improved at the end of treatmentcompared to baseline (FIG. 1).

During the study, no adverse events occurred, and tolerability of theproduct according to the Example 7 was judged as optimal by 100% ofpatients. The judgement of the patients was always very satisfactoryboth for the treatment easiness and for the organoleptic characteristicsof the product.

1-16. (canceled)
 17. A method of treating nail inflammatory diseasescomprising administering to a human or animal subject, an effectiveamount of a chitosan amino-polysaccharide and/or a physiologicallyacceptable salt thereof.
 18. The method of claim 17, wherein thechitosan amino-polysaccharide and/or a physiologically acceptable saltthereof is water soluble.
 19. The method of claim 18, wherein thechitosan amino-polysaccharide and/or a physiologically acceptable saltthereof exhibits a molecular weight greater than 50,000 Daltons.
 20. Themethod of claim 18, wherein the chitosan amino-polysaccharide and/or aphysiologically acceptable salt thereof exhibits a molecular weight from100,000 to 500,000 Daltons.
 21. The method of claim 18, wherein thechitosan amino-polysaccharide and/or a physiologically acceptable saltthereof is a hydroxyalkyl chitosan.
 22. The method of claim 21, whereinthe hydroxyalkyl chitosan is a hydroxypropyl chitosan.
 23. The method ofclaim 18, wherein the chitosan amino-polysaccharide and/or aphysiologically acceptable salt thereof is a carboxyalkyl chitosan. 24.The method of claim 17, wherein the nail inflammatory disease isselected from nail psoriasis, lichen planus, atopic dermatitis andalopecia areata.
 25. The method of claim 17, wherein the chitosanamino-polysaccharide and/or a physiologically acceptable salt thereof isadministered in combination with one or more active principles.
 26. Themethod of claim 25, wherein the active principle is selected fromcorticosteroids, keratolytic agents, non-steroidal anti-inflammatoryagents, anti-psoriatic agents, immunosuppressive agents, antisepticagents, moisturizers and nail strengthening agents.
 27. The method ofclaim 25, wherein the active principle is selected from bethametasone;budesonide; clobetasol and salts thereof; salicylic acid; benzoic acidand salts thereof; plant extract from Equisetum arvense; plant extractfrom Harpagophyton procumbens; diclofenac; aspirin; ketoprofen;calcipotriol; calcitriol; tretinoin; acitretin; tazarotene andcyclosporine.
 28. The method of claim 17, wherein the chitosanamino-polysaccharide and/or a physiologically acceptable salt thereof isadministered topically.
 29. The method of claim 28, wherein the chitosanamino-polysaccharide and/or a physiologically acceptable salt thereof isapplied to a nail surface freely, under semi-occlusive medication orunder occlusive medication.
 30. The method of claim 28, wherein thechitosan amino-polysaccharide and/or a physiologically acceptable saltthereof is administered by means of a topical formulation.
 31. Themethod of claim 30, wherein the topical formulation is a nail lacquer, aspray, a cream, an ointment, a gel, a lotion or a foam.
 32. The methodof claim 30, wherein the topical formulation comprises a chitosanamino-polysaccharide and/or a salt thereof, from 0.1 to 25 wt. % withrespect to the total weight of the formulation.
 33. The method of claim30, wherein the topical formulation comprises a chitosanamino-polysaccharide and/or a salt thereof, from 0.3 to 10 wt. % withrespect to the total weight of the formulation.
 34. The method of claim30, wherein the topical formulation comprises a chitosanamino-polysaccharide and/or a salt thereof, from 0.5 to 5 wt. % withrespect to the total weight of the formulation.